The Impact of Texas Red on Lipid Bilayer Properties

We investigated the impact of fluorescent labeling on the properties of a lipid bilayer using atomistic molecular dynamics simulation. The system consisted of 24 Texas Red 1,2-dihexadecanoyl-sn-glycero-3-phophoethanolamine (TR-DHPE) in a bilayer of 488 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipids. We found binding between TR DHPE and DPPC caused by electrostatic interactions. On average, TR DHPE is bound to 1.2 DPPC molecules. Binding reduced the diffusion coefficient of TR DHPE by 34% relative to unlabeled DPPC molecules. We estimate that binding would lead to a 5 C increase in the liquid to liquid-ordered transition temperature of a ternary lipid system. These results emphasize the importance of considering the impact of fluorescence labeling when interpreting experimental results.